1. Field of the Invention
The present invention relates to the treatment of pain and inflammation in body tissues. In particular, the present invention relates to methods and compositions for treating osteoarthritis using ion-channel regulators.
2. Discussion of the Background
Osteoarthritis is a degenerative joint disease in which cartilage and bone are primarily affected. Osteoarthritis is especially common among older people, and usually affects a joint on one side of the body. In osteoarthritis, the cartilage breaks down and wears away, causing pain, swelling, and loss of motion of the joint. Further details are provided in Osteoarthritis, National Institute of Arthritis and Musculoskeletal and Skin Diseases, National Institutes of Health, NIH Publication No. 02-4617, July, 2002 which is incorporated herein by reference.
Rheumatoid arthritis is a systemic disease which, when manifested in joints, primarily affects the synovial membrane. Rheumatoid arthritis begins at a younger age than osteoarthritis, is usually present bilaterally in the joints, and sometimes results in feelings of sickness, tiredness, and fever. Further details are provided in Rheumatoid Arthritis, National Institute of Arthritis and Musculoskeletal and Skin Diseases, National Institutes of Health, NIH Publication No. 04-4179, May, 2004 which is incorporated herein by reference.
Inflammation is a fundamental biological process consisting of a dynamic complex of cytologic and chemical reactions that occur in the affected blood vessels and adjacent tissues in response to an injury or abnormal stimulation caused by a physical, chemical, or biological agent. The process of inflammation includes: 1) local tissue reactions and resulting morphologic changes; 2) destruction or removal of injurious material; and 3) responses that lead to repair and healing. The so-called “cardinal signs” of inflammation are redness, heat (or warmth), swelling, pain and inhibited or lost function. All of these signs may be observed in certain instances, but no one of them is necessarily always present. A disease that involves inflammation is herein referred to as an “inflammatory disease”.
The proteins known as cytokines are important factors in the onset and maintenance of inflammation. Cytokines, which are produced by synovial lining cells, cartilage cells, as well as by other types of cells, regulate numerous biological responses, including cell growth, and the nature and extent of proteins that are made by cells. Cytokines include interferons (IFNs), colony stimulating factors (CSFs), interleukins (ILs), and tumor necrosis factors (TNFs). It is known that the presence of inflammatory cytokines (IL-1, IL-8, TNF) initiates a series of complex cellular and molecular events, including the expression of adhesion molecules, the production of secondary inflammatory mediators (prostaglandins, leukotrienes), and the production of growth factors.
Arthritis is an inflammatory disease characterized by inflammation of a joint, which term includes synovial tissue and membranes. There are many forms of arthritis, including without limitation, osteoarthritis (hypertrophic or degenerative arthritis), rheumatoid arthritis, arthritis due to infection (tuberculosis, Lyme disease, rheumatic fever, etc.), suppurative arthritis, juvenile arthritis, and gouty arthritis. Elevated tissue levels of IL-1, IL-8, and TNF are found in arthritis and in other inflammatory conditions.
In osteoarthritis, the cartilage that covers the ends of the bones that form the joint is slowly degraded by the action of various enzymes, particularly the matrix metalloproteinases (MMPs) which are secreted into the synovial fluid of the joint by the synovial lining cells in response to stimulation by various proinflammatory cytokines, particularly IL-1 and TNF. The destruction of cartilage by the MMPs perpetuates the inflammatory reaction and leads to the joint pain associated with osteoarthritis. Further details are provided in “Biochemistry and Metabolism of Articular Cartilage in Osteoarthritis”, H. J. Mankin and K. D. Brant, in Osteoarthritis: Diagnosis and Medical/Surgical Management, 2nd Ed., R. W. Moskowitz, D. S. Howell, V. M. Goldberg, and H. J. Mankin, W.B. Saunders Co., Philadelphia (1992), which is incorporated herein by reference.
Ion channels are glycoprotein structures located in the membrane of cells, including synovial cells and cartilage cells, which allow ions, particularly monovalent and divalent cations and anions, to pass through the membrane. Ion channels include but are not limited to calcium-ion channels, sodium-ion channels, potassium-ion channels, chloride-ion channels, cation-ion channels, anion-ion channels, connexon channels and non-selective ion channels.
Ion-channel regulators are a known group of agents, usually chemical in nature, that alter the entry of certain ions into or out of cells and cellular organelles, depending on whether the intracellular or extracellular concentration of the particular ion is greater, and on the electrical potential difference that exists between the inside and the outside of the cell. The combined effect of the concentration difference and the electrical potential difference is called the electrochemical gradient. When the gate of an ion channel is open, the ions will flow down their electrochemical gradient unless they are prevented from doing so as, for example, by means of a chemical ion-channel regulator. Ion-channel regulators that cause a reduction in the ion flow that would otherwise occur are referred to as “ion-channel blockers.” Ion-channel regulators that cause an increase in the ion flow that would otherwise occur are referred to as “ion-channel activators.”
Ion-channel regulators are commonly used for treating a variety of conditions, including cardiac conditions such as atrial fibrillation, supraventricular tachycardias, hypertrophic cardiomyopathy and hypertension, as well as migraine headaches, the prevention of brain damage, and other disorders. Certain ion-channel regulators and related compounds have been described in the art as being useful in the treatment of inflammatory diseases. For example, Thorpe et al. (U.S. Pat. No. 6,416,758) disclose antibody conjugate kits for selectively inhibiting VEGF binding to only one (VEGFR2) of the two VEGF receptors. The antibodies inhibit angiogenesis and induce tumor regression, and can be used for treatment of all conditions where angiogenesis is a factor (including arthritis). Thorpe, et al. mention CAI, an angiogenesis inhibitor that acts as a calcium-channel regulator that prevents actin reorganization, endothelial cell migration and spreading on collagen IV.
Stamler, et al. (U.S. Pat. No. 6,359,182) disclose C nitroso compounds derived from a wide variety of drugs, including known calcium channel regulators (verapamil, diltiazem, etc.). These derivatives provide relaxation and platelet inhibiting effects, and due to their NO donor finction, are said to be useful for treating arthritis.
Schonharting, et al. (U.S. Pat. No. 6,337,325) provide a combination preparation which includes a compound having a phosphodiesterase inhibiting action, and a compound which reduces the biologically effective intracellular Ca2+ content (such as verapamil). Their preparation can be used to treat rheumatoid arthritis.
Medford, et al. (U.S. Pat. No. 5,811,449) disclose a method for treatment of atherosclerosis and other cardiovascular and inflammatory diseases that are mediated by VCAM 1 (“vascular cell adhesion molecule 1”). The list of diseases includes rheumatoid arthritis and osteoarthritis. The dithiocarboxylates and other compounds used with the method can be attached to a large number of pharmaceutically-active compounds, including calcium-channel regulators (verapamil, diltiazem, nifedipine).
Certain known compositions for the relief of pain associated with inflammatory disease states may contain ion-channel regulators and related compounds. For example, Breault (U.S. Pat. Nos. 6,365,603 and 6,100,258) describes aromatic/phenyl compounds useful for inhibiting the pain enhancing effects of E-type prostaglandins. The compounds can be used to treat pain associated with rheumatoid arthritis, osteoarthritis, and osteoporosis, and may contain additional agents such as calcium-channel regulators.
Mak (U.S. Pat. No. 6,190,691) provides methods for treating several inflammatory conditions that are mediated by TNF production (including rheumatoid arthritis). Treatment is accomplished by administering a therapeutically effective amount of any of a number of compounds, including calcium-channel regulators such as verapamil, nicardipine or isradipine. Mak teaches direct injection of large amounts of (+)-verapamil (20-40 mg in a 10 mg/mL solution) into joints for the treatment of rheumatoid arthritis.
There is no known cure for osteoarthritis, and consequently clinical efforts aimed at treating it are presently directed toward symptomatic relief of pain. Conventional therapies include treatment with analgesics or non-steroidal anti-inflammatory drugs (aspirin, ibuprofen, naproxen, COX 2 inhibitors such as CELEBREX and VIOXX, and the like), interarticular injection of corticosteroids and unmodified or modified hyaluronan (a treatment called viscosupplementation), as well as the use of steroids, antibiotics, glucosamine, chondroitin, immunomodulators, and penicillamine. Traditional remedies such as the application of heat for temporary, local pain relief are helpful for some patients, and suitable exercise and physical therapy programs can help in maintaining joint mobility. Joint replacement surgery may be advised in severe cases.
Despite the availability of a wide range of medications and treatment modalities for arthritis and inflammatory diseases in general, as described above, none has proved to be entirely satisfactory for osteoarthritis. In particular, there remains a need for innovative treatments that target the underlying cause of osteoarthritis, for example the production of MMPs, and thereby help reduce, eliminate, or slow its progression (expressed symptomatically by bone erosion, cartilage erosion, inflammation, swelling, abnormal neovascularization, etc.).